Fixed blading of axial compressors

ABSTRACT

Fixed blading for an axial compressor constituted by a succession of blades fixed on at least one annular wall and a method of operating the same. Fluid passing through a passage between adjacent blades is drawn into a suction opening and the pressure at the suction opening is maintained substantially equal to the flow static pressure in the passage.

Unite States Patent [191 Qarriere et a1.

[451 Nov. 5, 1974 FIXED BLADING OF AXIAL COMPRESSORS [75] Inventors:Pierre P. Carriere, Paris; Jacky R.

Leynaert, Igny; Georges I). Meauze, Paris; Jean-Jacques Thibert,Verrieres-le-Buisson, all of France [73] Assignee: Office NationalDEtudes et de Recherches Aerospatiales (par abreviation: O.N.E.R.A.),France [22] Filed: Dec. 14, 1972 [21] Appl. No.: 314,965

[30] Foreign Application Priority Data Dec. 27, 1971 France 71.46854[52] US. Cl 415/1, 415/53, 415/145, 415/168, 4l5/DIG. l

[51] Int. Cl. F04d 29/68, F04d 27/02 [58] Field of Search 415/DIG. 1,168, 53, 144, 415/145, 121 A, l

[56] References Cited UNITED STATES PATENTS 2,291,828 8/1942 New415/D1G. 1 2,656,096 10/1953 Schwarz I 4l5/DIG. 1 2,682,363 6/1954Lombard et a1 415/DIG. 1 2,720,356 10/1955 Erwin 415/D1G. 1 FOREIGNPATENTS OR APPLICATIONS 504,214 4/1939 Great Britain 415/D1G. 1 619,7223/1949 Great Britain 415/53 Primary ExaminerHcnry F. Raduazo Attorney,Agent, or Firm-Larson, Taylor and Hinds [57] ABSTRACT Fixed blading foran axial compressor constituted by a succession of blades fixed on atleast one annular wall and a method of operating the same. Fluid passingthrough a passage between adjacent blades is drawn into a suctionopening and the pressure at the suction opening is maintainedsubstantially equal to the flow static pressure in the passage.

17 Claims, 4 Drawing Figures 7 .79 3 I \BWKN PATENTEU MY 5 I974 amassSHEE? l 9? 2 P/P/U/P A E 7 1 FIXED BLADING OF AXIAL COMPRESSORS Theinvention relates to fixed blading for axial compressors, such fixedblading being constituted by arrays of blades each comprising asuccession of blades borne by an annular lateral wall, or interposedbetween two annular lateral walls, this or these annular lateral wallsextending transversely between the blades of the array of blades.

The present invention also relates to a method of operating such anaxial compressor.

Among the more particularly advantageous applications of the invention,there may be mentioned the application to axial compressors for aircraftturboreactors.

It has already been suggested to form in the one or more annular lateralwalls suctionopenings arranged between two successive blades andconnected to aspirating means; these suction openings enabling thereduction of disturbances due to the boundary layer which is developedon this or these annular lateral walls.

In fact, these disturbances affect the two dimensional character of theflow and cause an increase in the losses undergone by the flow throughthe array of blades.

It is an object of the invention to provide a particularly advantageousshape and arrangement of these suction openings.

According to the invention each suction opening has elongated shape andextends over the whole width of the passage defined by two successiveblades, between an under surface region or intrados (side subjected toincreased pressure) of a blade situated towards the leading edge and aback surface region or extrados (side subjected to reduced pressure) ofthe following blade situated at one half or preferably one third of itslength, from its leading edge. 7

Due to the shape and arrangement of such aspirating openings, whichshape and arrangement have been perfected by applicant after numerousaerodynamic tests, it is possible to give the aspirated flow a suitablevalue to cause localised suction of the boundary layer enabling theelimination or considerable reduction of the disturbances due to thisboundary layer.

According to a preferred feature of the invention, the suction means arearranged so that the pressure at the level of the suction openings is ofthe same order of magnitude that is to say substantially equal to thestatic pressure of the local flow in the passage concerned.

The invention further relates to a method for operat- 7 ing such anaxial compressor wherein fluid aspired through the passages betweenadjacent blades is maintained at a pressure substantially equal to theflow static pressure in the passage.

The invention will in any case be well understood with the aid of theadditionaldescription which follows as well as of the accompanyingdrawings, which complement and drawings relate to various embodiments ofthe invention and are not of course to be regarded as limiting incharacter.

In the drawings:

FIG. 1 shows a partial diagrammatic perspective view of fixed bladingfor an axial compressor, constructed in conventional manner, and inwhich there are shown by various arrows the flow disturbed by theboundary layer which is developed on the annular lateral wall.

FIG. 2 shows, under the same conditions, this fixed blading constructedaccording to the invention and in which the flow represented by thevarious arrows is perfectly bidimensional.

FIG. 3 is a partially developed view of fixed blading constructedaccording to the invention.

Lastly, FIG. 4 is a diagrammatic section along the line lV-IV of FIG. 3.

The fixed blading shown in FIGS. I and 2 is constituted by an array ofblades comprising a succession of blades 1 borne by an annular lateralwall 2 on which said blades 1 are fixed by one of their two ends. Forclarity of the drawing there is shown a single annular lateral wall, butthe blades can also be interposed between two concentric annular lateralwalls.

In FIG. 1, there is involved conventional fixed blading and the boundarylayer which is developed on the annular lateral wall 2 causesdisturbances of flow in the passages defined by two successive blades;these disturbances are constituted by detachments and vortexes whichcreate an artificial convergence of the flow into the abovesaidpassages.

There is shown in this FIG. 1, by different arrows, the disturbed flowin the vicinity of the annular lateral wall 2. This disturbed flowinvolves the blade 1 over a considerable length since the orientation ofthe line L enveloping the zone affected by the detachments and thevortexes is about 45 with respect to the direction in which the bladeextends.

This being the case, there is formed in the annular lateral wall 2 or inthe two concentric annular lateral wallsa suction opening 3 connected tosuction means.

According to the invention, and as illustrated in FIG. 2, this suctionopening 3 has elongated shape and extends over the whole width of thepassage defined by two successive blades, between an under surfaceregion of one blade situated towards its leading edge and a back surfaceregion of the following blade situated at half or preferably one thirdof its length, from its leading edge.

It will be noted that the shape of the suction opening 3 is elongatedand oriented parallel to the isobars of the local pressure field andthat the arrangement of the suction opening 3 is such that said suctionopening 3 occurs in the passage concerned, in a region where thepressure gradients reach maximal values.

As regards the suction means which will be more explicitly consideredbelow it can be arranged so that the pressure at the level of thesuction openings is of the same order of magnitude as the staticpressure of the local-flow in the passage concerned.

As shown in FIG. 2, by different arrows, the flow in the fixed blading,constructed according to the invention, has a bidimensional characterover all of the blades, given that the boundry layer on the annularlateral wall 2 has been trapped and that the detachments and vortexeshave been eliminated.

In FIG. 3 there is shown a partial view of a planar gigg'egtion of thefixed blading shown in perspective in In the neighbourhood of theundersurface of the blade, the suction opening 3 has a rounded shape,whilst in the neighbourhood of the back surface of the following bladethe suction opening 3 has a shape matching the airfoil of the blade.From the constructional point of view, the suction opening 3 can beextended below the latter blade beyond its back surface, thecorresponding edge of this suction opening 3 then being bounded by thefraction of the back surface of the blade situated above the saidsuction opening.

In FIG. 4 there is shown in axial section the fixed blading of FIG. 3,the rotor of the compressor being denoted by the reference numeral A andthe two movable blade assemblies of the compressor, surrounding thefixed blade assembly according to the invention, being denoted by thereference numerals B and B respectively.

As shown in this FIG. 4, the suction opening 3 can include an upstreamedge 3a perpendicular to the annular lateral wall 2 in which it isformed, and a downstream edge 3b oblique and forming an acute angle withthe abovesaid wall. This arrangement facilitates the suction of theboundary layer.

As regards the suction means, they can be of different natures accordingto the conditions of use of the compressor.

In particular these suction means can be servocoupled, as regards thevalue of the flow aspirated, to various characteristics of thecompressor. In particular they can be servocoupled to the rotary speedso that the ratio of the flow aspirated to the flow of the streampassing through the compressor remains constant.

These suction means can, as shown in FIG. 4, comprise a buffer space 13from which the aspirated fluid is evacuated by means of a restrictingdevice comprising, for example, a fixed constriction 14 and/or aregulating valve '15.

This regulating valve 15 can then be governed by a regulator 16 actingas a function, on one hand, of the static pressure of the flow upstreamof the fixed blade assembly (which static pressure can be transmittedthrough an aperture 17 formed in a suitable place of the compressor)and, on the other hand, of the static through the suction opening, saidsuction means including means for maintaining the pressure in thesuction opening substantially equal to the flow static pressure in thesaid passage.

2. Fixed blading according to claim 1, wherein each suction openingcomprises an upstream edge perpendicular to the annular lateral wall andan oblique downstream edge forming an acute angle with the abovesaidannular lateral wall.

3. Fixed blading according to claim 1, wherein each suction openingcomprises a porous or perforated wall arranged to limit the aspiratedflow-rate.

4. An aircraft turboreactor axial compressor, comprising fixed bladingaccording to claim 1.

5. Fixed blading according to claim 1, said suction means includingmeans for maintaining constant the ratio of the flow rate of the fluidaspired through the said suction opening to the flow rate of the fluidflowing through the said passage.

6. Fixed blading according to claim 1, said suction means including aregulator device operatively connected to the suction opening toregulate the suction pressure as a function of a particular pressure ofthe suction pressure (static pressure transmitted by an aperture 18formed in the buffer space 13).

In certain cases, there may be provided a porous or perforated wall 19(shown in mixed line in FIG. 4), arranged in the suction opening 3 andlimiting the flowrate of aspiration.

The flow of fluid aspirated by the group of suction openings 3 can beejected to the atmosphere, or advantageously be used for other purposes.

This latter possibility is particularly advantageous when it relates tothe application of the invention to axial compressors for aircraftturbo-reactors; the fluid aspirated from the fixed blade assemblythrough the suction openings can be used as a driving fluid, or even asa cooling fluid for other members (turbine, airconditioning apparatus,etc.). It will be noted that this arrangement then renders unnecessarythe take-off members generally provided in such compressors.

The fluid sucked into the fixed blade assembly can also be reinjectedfurther upstream into the compressor by means of a suitable devicearranged to obtain a blast or parietal effect with a view to reabsorbingpossible by a succession of blades fixed on at least one annular wall,each passage between two adjacent blades being provided with a suctionopening, suction means associated with said suction opening for aspiringfluid flow passing through the passage.

7. Fixed blading according to claim 1, including means for exhausting tothe atmosphere the fluid aspirated through the suction opening.

8. Fixed blading according to claim 1, including means for deliveringthe fluid aspired through the suction opening to at least one otherstage of the compressor situated upstream from said fixed blading forproducing thereat a control effect on the boundary layer by a blasteffect.

9. Fixed blading according to claim 1, said suction opening having anelongated shape extending across the whole width of said passage betweenan undersurface region of one blade situated towards its leading edgeand a back surface region of the following blade situated in the firsthalf of its length from its leading edge.

10. Fixed blading according to claim 9, wherein the suction openingextends between an undersurface region of a blade situated towards itsleading edge and a back surface region of the following blade situatedabout two thirds of its length from its leading edge.

11. Fixed blading according to claim 1, said suction means including abuffer space adjacent the suction opening for receiving the fluidpassing therethrough.

12. Fixed blading according to claim 11, including an exhaust means forcontrollably delivering fluid out of said buffer space, and meansresponsive to the flow static pressure in the passage and to thepressure in the buffer space for controlling the flow rate through theexhaust means.

13. A method of operating an axial compressor of the type constituted bya succession of fixed blades fixed on at least one annular wall of thecompressor, comprising the steps of:

aspiring fluid from each passage between two adjacent blades through asuction opening,

and maintaining the pressure in the suction opening substantially equalto the flow static pressure in the passage.

14. A method according to claim 13, including delivering the fluidaspired through the suction opening into a buffer cavity, controllablydelivering the fluid out of the buffer cavity, sensing the static flowpressure in the passage, sensing the pressure in the buffer cavity, andcontrolling said delivery in response to both of said sensed pressures.

15. The method of claim 13, including maintaining constant the ratio ofthe flow rate through the suction opening to the flow rate of fluidthrough the passage.

1. Fixed blading for an axial compressor constituted by a succession ofblades fixed on at least one annular wall, each passage between twoadjacent blades being provided with a suction opening, suction meansassociated with said suction opening for aspiring fluid through thesuction opening, said suction means including means for maintaining thepressure in the suction opening substantially equal to the flow staticpressure in the said passage.
 2. Fixed blading according to claim 1,wherein each suction opening comprises an upstream edge perpendicular tothe annular lateral wall and an oblique downstream edge forming an acuteangle with the abovesaid annular lateral wall.
 3. Fixed bladingaccording to claim 1, wherein each suction opening comprises a porous orperforated wall arranged to limit the aspirated flow-rate.
 4. Anaircraft turbo-reactor axial compressor, comprising fixed bladingaccording to claim
 1. 5. Fixed blading according to claim 1, saidsuction means including means for maintaining constant the ratio of theflow rate of the fluid aspired through the said suction opening to theflow rate of the fluid flowing through the said passage.
 6. Fixedblading according to claim 1, said suction means including a regulatordevice operatively connected to the suction opening to regulate thesuction pressure as a function of a particular pressure of the flowpassing through the passage.
 7. Fixed blading according to claim 1,including means for exhausting to the atmosphere the fluid aspiratedthrough the suction opening.
 8. Fixed blading according to claim 1,including means for delivering the fluid aspired through the suctionopening to at least one other stage of the compressor situated upstreamfrom said fixed blading for producing thereat a control effect on theboundary layer by a blast effect.
 9. Fixed blading according to claim 1,said suction opening having an elongated shape extending across thewhole width of said passage between an undersurface region of one bladesituated towards its leading edge and a back surface region of thefollowing blade situated in the first half of its length from itsleading edge.
 10. Fixed blading according to claim 9, wherein thesuction opening extends between an undersurface region of a bladesituated towards its leading edge and a back surface region of thefollowing blade situated about two thirds of its length from its leadingedge.
 11. Fixed blading according to claim 1, said suction meansincluding a buffer space adjacent the suction opening for receiving thefluid passing therethrough.
 12. Fixed blading according to claim 11,including an exhaust means for controllably delivering fluid out of saidbuffer space, and means responsive to the flow static pressure in thepassage and to the pressure in the buffer space for controlling the flowrate through the exhaust means.
 13. A method of operating an axialcompressor of the type constituted by a succession of fixed blades fixedon at least one annular wall of the compressor, comprising the steps of:aspiring fluid from each passage between two adjacent blades through asuction opening, and maintaining the pressure in the suction openingsubstantially equal to the flow static pressure in the passage.
 14. Amethod according to claim 13, including delivering the fluid aspiredthrough the suction opening into a buffer cavity, controllablydelivering the fluid out of the buffer cavity, sensing the static flowpressure in the passage, sensing the pressure in the buffer cavity, andcontrolling said delivery in response to both of said sensed pressures.15. The method of claim 13, including maintaining constant the ratio ofthe flow rate through the suction opening to the flow rate of fluidthrough the passage.
 16. The method of claim 13, including the step ofdelivering the aspired fluid to the atmosphere.
 17. The method of claim13, including delivering the aspired fluid to at least one stage of thecompressor upstream of the fixed blading to produce thereat a controleffect on the boundary layer by a blast effect.